Process for preparing fabrics



April 25, 1967 s. M. IBRAHIM 3,315,323

PROCESS FOR PREPARING FABRICS Filed Aug. 5. 1963 STRETCH ELASTIC YARN PREDETERMINED AMOUNT HEAT-SET ELASTIC YARN AT EXTENDED LENGTH PLY HEAT-SET ELASTIC YARN WITH INELASTIC YARN lN FULLY EXTENDED STATE INCORPORATE PLIED YARN IN FABRIC WITH PLIED YARN IN FULLY EXTENDED STATE HEAT- RELAX FABRIC INVENTOR SALIM M. IBRAHIM BY W ATTORNEY United States Patent O 3,315,328 PRGCESS FOR PREPARING FABRICS Salim M. Ibrahim, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Aug. 5, 1963, Ser. No. 299,817 6 Claims. (Cl. 28-72) This invention relates to a process for preparing elastic fabrics. More particularly, it relates to a process for preparing elastic fabrics which exhibit a high degree of elasticity at relatively low levels of power or retractive force.

Until recently, elastic fabrics available to the textile industry have been relatively heavy and bulky. The use of such fabrics has been generally confined to garments where the benefits accruing to the wearer were those of high restraining power rather than attractive aesthetics. Recently, with the advent of spandex fibers, which can be spun in fine deniers, bulk and weight of elastic fabrics have been reduced. The spandex fibers are particularly desirable for use in foundation garments and surgical hosiery but, due totheir high degree of restraining power, incorporation of these fibers in textile fabrics such as suitings, dresswear, mens hosiery, and other textile goods has been somewhat limited. Economic factors have also restricted the use of spandex fibers since these fibers are, in general, more expensive than the inelastic fibers.

It is, therefore, an object of this invention to provide a process for preparing elastic fabrics which have a high degree of elasticity at relatively low levels of retractive force. It is another object of this invention to provide a process for preparing such fabrics which utilizes a minimum quantity of the more expensive spandex fiber yet provides aesthetically desirable fabrics which have desirable elastic properties.

In general, the objects of this invention are achieved by a process which comprises stretching an elastic yarn containing spandex filaments a predetermined amount, heatsetting the elastic yarn in its extended condition, plying the heat-set elastic yarn with an inelastic yarn while maintaining the heat-set elastic yarn in a fully extended condition, and thereafter incorporating the plied yarn in a fabric while maintaining the plied yarn in its fully extended state. After preparation of the fabric, the heat-set elastic component is relaxed. Surprisingly, a fabric having a smooth surface with excellent stitch definition is obtained by this process. This is in contrast to the pebbly, uneven etfect which would be expected to result due to the inelastic yarn buckling about the elastic component. Not

only are the fabrics more aesthetically desirable thanthose heretofore produced, but also by maintaining the elastic component in its extended condition and plying the elastic component with a yarn comprised entirely of inelastic fibers the quantity of the expensive, elastic fiber required is substantially reduced. Thus, fabrics made according to this invention possess both economic and aesthetic advantages.

A preferred process is set forth in the form of a flow sheet in the accompanying drawing. Each of the steps will be explained in detail in the discussion which follows.

In practicing the present invention, the elastic yarn which contains the spandex filaments may be prepared from a variety of fibers which may be combined in a number of different forms. The inelastic, fibers may be either natural or synthetic fibers, e.g., cotton, wool, silk, polyesters, polyamides, acrylic fibers, polyhydrocarbon fibers, cellulose derivatives, or blends of two or more inelastic fibers. The elastic fibers are those of the spandex type, preferably those prepared from segmented polyurethanes as described in US. Patents 2,929,800, 2,929,801, 2,929,802, 2,929,804, 2,953,839, 2,957,852,

and 3,097,192. These spandex fibers when in filament form have elongations greater than 150%, tensile recovery of and a stress decay of less than about 20%.

The preferred form of elastic yarn is a composite corespun yarn made by combining a continuous filament elastic yarn with one or more rovings of inelastic staple fibers. These yarns may be prepared as described in US. Patents 2,024,156, 3,017,740, and 2,038,295. Alternatively, the elasticyarn may be comprised of a blend of inelastic fibers and spandex fibers such as is disclosed in US. 3,007,227. In addition, helically wrapped yarn in which an inelastic fiber covering is wrapped about a continuous spandex filament core may also be used.

The inelastic yarn which is plied with the elastic yarn is prepared entirely from inelastic fibers of the types previously described. This yarn may be in continuous filament or spun-yarn form, depending on the characteristics desired in the final fabric. A combination of continuous filaments and staple fibers may also be used.

In carrying out the steps of the process of this invention, the elastic yarn is first stretched a predetermined amount. As a general rule, it is preferred that the elastic element be stretched an amount approaching but not exceeding its elastic limit. While maintaining the elastic yarn in its extended condition, it is heat-set by following the teachings of Canadian Patent 621,569. The teaching of this patent is incorporated herein by reference. The heat-setting treatment should be of a relatively mild order such that the elastic component in the yarn is stabilized or heat-set temporarily in its elongated condition. The treatment should not be so severe as to permanently stabilize the elastic component. Mild heat-setting treatments, e.g., treatment in boiling water or steam at 10 pounds per square inch, initially stabilize the elastic component but permit retraction of from 30% to 60% when the final fabric is relaxed to unlock the elastic component. Those skilled in the art can readily select heat-setting conditions which will provide a desired balance of elasticity and power in the final fabric. In addition to boiling the fabric to unlock the elastic component and impart elasticity to the finished fabric, various fabric finishing processes such as scouring and dyeing may be used.

After the heat-setting treatment, the elastic yarn is then plied with the inelastic yarn. Because of the relative mildness of the heat-setting conditions employed, the elastic yarn may not be entirely stable but may have a tendency to retract although to a lesser extent than before it was heat-set. Therefore, it is important to the successful practice of this invention that the elastic yarn be maintained at maximum extension while it is being plied with the inelastic yarn. Alternatively, the elastic yarn and the inelastic yarn may be plied before the heat-setting treatment. After plying, the yarns can then be heat-treated to stabilize the elastic component. This procedure is not preferred for some yarns since the inelastic yarn will be subjected to the heat-setting process which may possibly produce an undesirable effect on the aesthetic characteristics of the inelastic yarn.

After plying the heat-set elastic yarn and the inelastic yarn, the plied yarn is incorporated in the fabric by Weaving, knitting, or other fabric-forming operations. 'In order to avoid non-uniformities in the finished fabric, it is necessary that the plied yarn be under suflicient tension to maintain the elastic component at maximum extension. Since the elastic component is at least semi-stabilized and its elasticity at least partially immobilized, problems associated with tension control and uniformity of yarn feed are minimized.

In the following examples, yarn power, which is a measure of the resistance to stretch of the yarn expressed in grams per denier of the elastic component only, is measured at specified selected points based on the ex- In determining sock power, a ooped specimen four inches wide is cut from the leg of a :ock and is cycled three times between zero and 7.5 inches ising a constant rate of extension tensile tester, i.e., an instron tester. Power is measured at an extension of 5 nches on the first cycle recovery curve. It is reported n pounds per inch, i.e., the ratio of the load required hold the looped specimen at a -inch extension divided 9y the width of the specimen in inches. The 5-inch extension point is considered to be representative of the power exerted by the sock on the leg of a person.

ended length of the yarn.

Example I This example illustrates the preparation of mens socks by the process of the present invention.

A 70-denier (7.78 tex.) spandex yarn is prepared as described in U.S. 3,039,895. A commercially available acrylic tow, the individual filaments of which have a denier of 3 (0.33 tex.), is reduced to staple fibers on a Turbo Stapler as described in US. 2,748,426. The acrylic fibers are then completely relaxed in an autoclave by alternating cycles of steam and vacuum, and the relaxed fibers are used to prepare a roving, all according to conventional practice. The continuous filament spandex yarn and the roving of acrylic fibers are then combined to form a core-spun composite elastic yarn by the procedure described in US. 3,038,295. In this operation, the spandex yarn under an extension of 4 is fed to the front rolls of a conventional spinning frame, where it is combined with the roving of acrylic fibers to produce a composite yarn equivalent to we. (49.2 tex.) with a twist of 5 .4 t.p.i. Z. By weight, the composition of the composite yarn is 95.6% acrylic fiber and 4.4% spandex yarn. The elastic yarn is then rewound from the spinning bobbins onto solid dye tubes under suificient tension to maintain the extension of the elastic core element and is then heat-set in an autoclave with a cycle of minutes of vacuum, 30 minutes of steam at 240 F. (10 p.s.i.), and 10 minutes of vacuum. A roving of the acrylic fibers is spun by conventional procedures to provides a ,4 w.c. (55.3 tex.) yarn with a twist of 5.4 t.p.i. Z. The heatset composite elastic yarn A and the inelastic yarn B are then plied with a twist of 3.0 t.p.i. S to form a plied yarn C. During the plying step the elastic yarn is maintained in its fully extended condition. Power values determined for the yarns are set forth in Table l, which follows:

After plying, yarn C is Wound onto cones and waxed in a conventional manner and then fed one end to each feed of an 84-needle Komet knitting machine. Mens socks are knit in a 2 x 2 rib stitch. The socks are dyed and dried. The power of the finished socks is 0.05 lbs./ in. The finished socks are smooth and uniform in texture and are free from streaks and unevenness. The power of 0.05 lb./in. is in the desired range for mens socks.

Example 11 This example illustrates the preparation of elastic fabric by a prior art process.

A 70-denier (7.78 tex.) spandex yarn is prepared as described in US. 3,039,895. A commercially available acrylic tow, the individual filaments of which have a denier of 3 (0.33 tex.), is reduced to staple fibers on a Turbo Stapler as described in US. 2,748,426. The acrylic fibers are then completely relaxed in an autoclave by alternating cycles of steam and vacuum and the relaxed fibers are used to prepare a roving, all according to conventional practice. The continuous filament spandex yarn and the roving of acrylic fibers are then combined to form a corespun composite elastic yarn by the procedure described in US. 3,038,295. In this operation, the spandex yarn under extension of 4x is fed to the front rolls of a conventional spinning frame, where it is combined withthe roving of acrylic fibers to produce a composite yarn equivalent to we (49.2 tex.) with a twist of 5.4 t.p.i. Z. By weight, the composition of the composite yarn is 95.6% acrylic fiber and 4.4% spandex yarn. The yarn is then rewound from the spinning bobbins to cones under sufficient tension to maintain the extension of the spandex core The yarn is waxed in a conventional manner in the course of rewinding. Two ends of this yarn are supplied to each feed of an 84-needle Komet knitting machine and knit as mens hose in a 2 x 2 rib stitch. In the relaxted condition after knitting, the length of the socks is 10.3 in. from the top of the leg to the heel gore and 10.7 in. from the toe to the heel gore. The socks are then given a boil-off for 2 hours in a detergent bath to simulate commercial dyeing and dried in a tumble dryer for 45 minutes at F. After this treatment, the lengths in the relaxed condition as above are 5.2 in. for the leg and 5.9 in. for the foot. These socks are commercially unacceptable for two reasons. First, although their length in the stretched condition (18 in. in the leg and 19 in. in the foot) is acceptable for wear, their small size in the relaxed condition makes them unpresentable on a store counter. Second, the excessive power of the socks causes them to be uncomfortably binding on the foot of the wearer. The power of these socks by the test previously described is 0.23 lb./ in.

Example III This example illustrates the ineffectiveness of a preboarding treatment in providing acceptable elastic properties in mens socks.

Additional socks are knit following the procedure of Example II. To provide a commercially acceptable relaxed length, the socks are given a pre-boarding treatment in an autoclave in the same'manner as commonly used for womens hoisery and mens hose made from inelastic fibers such as nylon. It is found that a pre-boarding treatment in excess of 5 minutes at 240. F. (10 p.s.i. steam) is necessary to achieve dimensional stability. This procedure does not provide a satisfactory solution because (a) the excessive pre-boa-rding time is economically unacceptable for commercial operations, (b) the high temperature and long exposure time have an adverse effect on the acrylic fibers and consequently on the tactile aesthetics of the finished socks, and (c) the power of the socks (0.18 lb./in. by the test previously described) is excesslve.

Example IV This example illustrates the preparation of mens socks by a process which omits the heat-setting step. The starting materials and procedures of Example II are used to prepare a composite elastic yarn A equivalent to ,4, w.c. (26.0 tex.) with a twist of 9.5 t.p.i. Z. By weight, this yarn is 912.5% acrylic fiber and 7.5% spandex fiber. The same roving of acrylic fiber is used to prepare conventionally a totally inelastic yarn B of w.c. (29.6 tex.) with a twist of 9.5 t.p.i. Z. Yarn A under maximum extension is plied with yarn B with a ply twist of 5.5 t.p.i. S. The plied yarn C is 96.5% acrylic fiber and 3.5% spandex fiber, by weight. One end of plied yarn C is supplied to each feed of a l32-needle Komet knitting machine. By conventional procedures, socks are knit, dyed, and dried on hosiery frames or Example V This example illustrates the preparation of mens socks from heat-set but unplied elastic yarns and inelastic yarns.

The yarns of Example IV are used in this example. Composite elastic yarn A is heat-set according to the procedure of Example I, except that the steam cycle is for 20 minutes rather than 30 minutes. Samples of heat-set yarn A and non-heat-set yarn B are boiled-off for 30 minutes in a relaxed condition with a consequent retraction of 45% for heat-set composite elastic yarn A and 3% for non-heat-set inelastic yarn .B. One end of each yarn, is supplied to each feed of the l32-needle Komet knitting machine of Example IV. Socks are knit, dyed, and dried as in Example IV. The finished socks have an unacceptably streaky and uneven texture and appearance because of the large difference in retraction of the elastic and inelastic yarns in dyeing and finishing.

Example VI This example illustrates the preparation of elastic fabric by the process of the present invention.

The yarns of Example IV are used in this example. Yarn A is heat-set as in Example V. The heat-set composite elastic yarn A and the inelastic yarn B are plied with a twist of 5.5 t.p.i. S. The plied yarn C is 96.5% acrylic fiber and 3.5% spandex fiber by weight. In the plying operation, the composite elastic yarn A is under sufiicient tension to maintain the elastic core element at maximum extension. One end of the plied yarn C is supplied to each feed of the l32-needle Komet knitting machine of Example IV. Dyeing and finishing of socks is the same as for Example IV. The finished socks of this example are entirely smooth and uniform in texture and appearance and have additional aesthetic advantages of softness and bulk as compared with the socks of Example IV. These socks illustrate the surprising aspect of this invention, namely, the freedom from streaks, unevenness or other surface distortion despite the fifteenfold difference in retraction of the two plies of the plied yarn in the course of dyeing and finishing of the socks. This highly desirable result is entirely unexpected in view of the fact that the textile industry has for many years made widespread use of differential retraction specifically to produce irregular surface elfects in fabrics. An acceptable power level of 0.07 lb./in. is achieved in the socks of this example with a relatively economical use of 3.5% spandex yarn.

Example VII This example illustrates the preparation of elastic fabric using spandex staple fiber Ibut omits the heat-setting and the plying steps of this invention.

A spendex tow with an individual filament denier of 6 (0.67 tex.), prepared as described in US. 3,077,006, is combined with a commercially available acrylic tow with an individual filament denier of 3 (0.33 tex.) according to the procedure of US. 3,077,006 to prepare a sliver blend of inelastic and elastic staple fibers. Additional totally inelastic slivers are prepared by conventional procedures from the same acrylic tow. In conventional worsted processing, the two kinds of sliver are combined to produce a w.c. (49.2 tex.) yarn with a twist of 5.4 t.p.i. Z. The composition of the yarn is 96% acrylic fiber and 4% spandex fiber. This composition is selected 7 from previous experience to insure uniform distribution of the elastic staple fibers in the yarn and to avoid nonuniform stretch in the yarn caused by dead spots" containing no elastic staple fibers. Two ends of this yarn are plied with a twist of 3.5 t.p.i. S. One end of the plied yarn is supplied to each feed of an 84-needle Komet machine for knitting of socks in a conventional manner. It

is recognized from other work that the spandex fiber content of 4% will provide execessive power in the finished socks unless this excessive power is destroyed. A conventional pre-boarding openation is used. It is found that times in excess of 5 minutes at 240 F. (10 p.s.i. steam) are required to provide dimension-a1 stability at a relatively high power level (0.14 lb./in.). The socks exhibit undesirably harsh aesthetics due to the effect of the heat-setting treatment on the acrylic fibers.

Example VIII This example illustrates the preparation of fabric by the process of the present invention.

The w.c. (49.2 tex.) composite elastic yarn of Example VII (yarn A) is wound at full extension on dye tubes and heat-set in an autoclave for 15 minutes at 228 F. (5 p.s.i.). The heat-set yarn is then plied with the A w.c. (55.3 tex.) inelasic yarn of acrylic fibers of Example I (yarn B) under sufiicient tension to maintain the composite elastic yarn at the extension at which it was heatset. The twist of the plied yarn is 3.0 t.p.i. S. One end of the plied yarn C is supplied to each feed of an 84-- needle Komet knitting machine and socks are knit, dyed, and boarded in a conventional manner. Finished socks have a power of 0.05 lb./in. and excellent visual and tactile aesthetics. Thus, elastic spun yarns can be prepared with a content of elastic staple fibers sufiiciently high to insure uniform stretch and uniform distribution, then, by practice of this invention, the elastic fiber content can be diluted to economical levels by plying with a yarn of inelastic fibers. At the same time, suitably low power levels can be achieved by heat-setting of the elastic spun yarn and the economic penalty minimized because of the relatively low percentage of elastic fiber in the final plied yarn.

Example IX In this example the heat-setting step is omitted.

Following the procedure of Example 11, a core-spun composite elastic yarn is made with a core of 70-denier (7.78 tex.) spandex yarn and a sheath of commercially available acrylic staple fibers with a filament denier of 1.5 (0.17 tex.). The spandex core is under an extension of 4X at the time of covering by the sheath'fibers. The composite yarn is equivalent to 30/1 co. (19.7 tex.) and has a twist of 17 t.p.i. Z. An inelastic yarn of the same count and twist is made from a blend of of the same acrylic staple fiber and 20% cotton. These two yarns are woven as alternate picks in a plain-weave fabric with a loom construction of x 54. The warp yarn is 40/1 cc. (14.8 tex.) with a twist of 22 t.p.i. Z, made from the same 80/20-acrylic fiber/cotton blend as the inelastic filling yarn. After conventional dyeing and finishing, the fabric has a ridged, puckered appearance similar to a seersucker fabric, illustrating one of the surface effects commonly obtained when yarns having a substantial difference in retraction characteristics are woven in the same fabric. The alternate picks of composite elastic yarn impart to the fabric a high degree of elasticity in the filling direction and a power level excessive for the uses to which a plainwoven fabric of this construction would ordinarily be put.

Example X are used to make a core-spun composite elastic yarn (yarn A) equivalent to 60/1 cc. (9.84 tex.) with a twist of 25 t.p.i. Z. This yarn is wound on dye tubes and heat-set by the procedure of Example I with a steam cycle of 20 minutes at 240 F. (10 p.s.i. steam). The 80/20- acrylic fiber/ cotton blend of Example IX is likewise spun to 60/1 cc. (9.84 tex.) with a twist of 27 t.p.i. S (yarn B). The heat-set composite elastic yarn A and the inelastic yarn B are plied to form a 60/2 cc. yarn C with a twist of 16 t.p.i. Z. In the plying operation, yarn A is I] ider suflicient tension to maintain the elastic core at Le extension at which it was heat-set. The plied yarn C woven as every pick in the warp of Example IX to vrrn a plain-Weave fabric with a loom construction of x 54. After conventional dyeing and finishing, the tbric is free of puckers, ridges or other surface distorons, despite the fact that each pick contains both elastic ad inelastic elements with different degrees of retraction uring fabric finishing. Also, despite the presence of re elastic element in every pick, the levels of power nd elasticity for this fabric are less than for the fabric f Example IX, and are suitable for imparting a mild egree of elasticity to a conventional plain-woven fabric )1" its characteristic uses.

Examples XI-X V These examples illustrate the reduced power levels nd the dimensional stability imparted to finished fabrics y the practice of this invention. Various yarns are preared, in general, by the same procedures and from the ame starting materials as in Example I, with variations .s indicated in Table 2, which follows.

In Example XI the composite elastic yarn is not heatet either before or after plying the 'ineslastic yarn.

In Examples XII, XIII, XIV, and XV, the composite lastic yarns are heat-set at 240 F. p.s.i. steam) for be time indicated in Table 2.

8 that, although the socks are stabilized against shrinkage, they retain adequate elasticity to meet commercial requirements for ease of donning and doffing.

Example XVI This example illustrates the range of power levels that can be obtained in finished fabric by varying the conditions under which the composite elastic yarn is heat-set. The starting materials and procedure of Example I are used to make a core-spun composite elastic yarn A equivalent to 1/20 w.c. (44.3 tex.) with a twist of 6 t.p.i. Z. The 70denier (7.78 tex.) spandex core element is extended 4 at the time of combining with the roving of inelastic acrylic fibers. The composite elastic yarn A is wound on dye tubes and heat-set in an autoclave at 240 F. (10 p.s.i. steam) by the general procedure of Example I for the times indicated in Table 3, which follows. The heat-set composite elastic yarn A is then plied with an inelastic yarn B of'acrylic fibers of 1/16 w.c. (55.3 tex.) with a twist of 6 t.p.i. Z. The twist in the ply yarn C is 3:5 t.p.i. S. One end of the plied yarn C is supplied to each feed of an 84-needle Komet knitting machine, and socks are knit, dyed and finished in a conventional manner. The power of the socks in lbs./in., determined by the test previously described, is recorded in Table 3.

TABLE 2 Example XI XII XIII XIV XV Elastic Composite Yarn A:

Denier of spandex core 70 70 70 70 Draft of core when covered 4X 4X 4X 4X X Equivalent yarn count:

W. c 1/2 1/20 1/20 1/34 1/34 Tex-.- 44. 3 44. 3 44. 3 26. 0 26. 0 Twist t.p.i. Z 6 6 9. 5 9. 5 Composition by weight, percent Acrylic sta e 95. 6 95. 6 95. 6 92. 5 95.1 Spandex core 4. 4 4. 4 4. 4 7. 5 4. 9 Duration of heat-setting in min at 240 F.

(10 p.s.i. steam) None 20 30 20 1 inelastic Yarn B:

Yarn count:

W. 1/l6 1/16 1/16 1/30 1/30 Tex 55. 3 55. 3 55. 3 29. 6 29. 6 Twist, t.p.i. "Z" 6 6 6 9. 5 9. 5 Ply Yarn C:

Twist, t.p.i. S 3. 5 3. 5 3. 5 5. 5 5. 5 Composition by weight, percent Acrylic staple 98 98 98 96. 5 97. 8 Spandex core 2 2 2 3. 5 2. 2 Yarn Power, in grams per denier at indicated percent of extended yarn length: Yarn A before heat-setting:

O. 015 0. 037 0. 056 0. 051 0. 088 0. 108 0. I35 0. 271 0.248 Knitting to Socks, Komet machine, needles--- 84 132 132 Relaxed Length of Leg (Top to Heel Gore), 7 Initial 10.3 12. 0 12. 6 12. 3 12. 5 After boil-ofi for-- 1 min 6. 5 9. 0 9. 9 9. 5 8. 8 3 min 6. 0 9.0 10. 2 8.5 9. 3 5min 5.9 8.7 9.0 8.7 9.0 10 min 5. 9 8. 5 10. 0 8. 3 8.9 30 min-- 5. 9 8. 8 9. 5 8. 4 8. 6 min--- 5. 9 8. 2 8. 8 8. 0 8. 3 min--- 5. 8 8. 0 8. 7 8.0 8. 2 300 min 5. 9 8. 2 8. 6 8.0 8. 2 Stretched Length of Leg (Top to Heel Gore),

Initial 21. 5 22 22. 5 22 22 After boil-ofi for 300 min 20 20. 2 19. 5 19 The reduction in power of the plied yarn as a consequence of the combination of heat-setting and plying is evident from the table. Since all socks were knit in the same construction on the knitting machine, the dimensional stability imparted by heat-setting of yarn A is indicated by the measurements for the length of the sock in the relaxed condition both immediately after knitting and after the indicated times of boil-off. The measurements of length of the socks in the stretched state show TABLE 3 Duration of heat-setting of 70 yarn A at 240 F. Power of socks, (10 p.s.i. steam), min.: lbs/in. 0 0.130 10 0.055 20 0 045 Example XVI shows control of power level by manipulation of only one variable, namely, time of exposure to a given heat-setting temperature. However, it is apparent from Canadian Patent 621,569 and from the discussion herein'before that the power level of the finished fabric or garment is directly dependent on the elimination of part of the available power of the spandex element of composite yarn A. This reduction is governed by a number of factors, including (a) the extent to which the spandex component is diluted by the inelastic component of yarn A and by the inelastic fibers of yarn B, (b) the extension at which composite yarn A was heatset, (c) temperature of heat-setting, (d) duration of heat-setting, and (e) nature of the heat-setting medium, e.g., hot water, hot air, steam under pressure, or various chemical agents at various temperatures. It is to be understood that all of these factors may be varied in the practice of the present invention as necessary to achieve the desired properties in the final fabric or garment.

Examples X VII-XXII These examples illustrate the application of the present invention in combination with other techniques for the production of novelty elastic yarns. The yarns used in these examples are as follows:

Yarn X-The 70-denier (7.78 tex.) spandex yarn of Example I.

Yarn YA w.c. (44.3 tex.) yarn with a twist of 6 t.p.i. Z, made from a blend of the acrylic fiber of Example I with wool. By weight, the yarn is 70% acrylic fiber and 30% wool. The yarn is spun by conventional procedures on the worsted system.

Yarn Z-A core-spun composite elastic yarn, made as in Example I from the spandex yarn of Example I and the roving of 70/30 acrylic fiber/wool used in making Yarn Y. The composite yarn is equivalent to we. (44.3 tex.) and has a twist of 6 t.p.i. Z.

These three yarns are combined in various ways on a conventional twister. In each instance, the tension (hence, the stretch) of one or more of the yarns is varied during plying, as indicated more fully in Table 4, which follows, to produce a series of novelty yarns. For instance, the stretch of elastic yarns X and Z is varied from zero to 400% or greater. The apparatus for and manner of varying the stretch are not critical or limited; 45 numerous devices and procedures known in the art may be used for'this purpose. The variables employed and the yarns produced are outlined in Table 4.

fore being combined with a roving of inelastic fibers to form a core-spun composite elastic yarn, and the corespun yarn may then be mildly heat-set.

(c) Yarn Z may be subjected to varying stretch then mildly heat-set before plying.

(d) Final plied yarns, incorporating one or more elements that have already been subjected to varying stretch, illustrated by but not limited to the yarns of Examples XVII to XXII, may be mildly heat-set.

In all of these applications, a mild heat-setting treatment will stabilize the varying stretch characteristics of the yarn involved and will make it easier to handle the variable-stretch yarn in such operations as plying, knitting and weaving. As taught by the present invention, heat-setting will tend to reduce the power of the finished fabrics. Obviously, by the same mechanism, it will reduce to some extent the novelty effect in the yarns and fabrics. By proper manipulation of the amount of varying stretch and the other governing factors previously discussed herein, any desired balance can be achieved between fabric power and novel surface effects.

In addition to the improvements already discussed, other advantages are obtainable with the heat-set/ply technology of the present invention. By the use of ply yarns wherein only one ply is elastic in character desirable improvements in the final fabric can be achieved by selection of proper direction of twist both in the component singles yarns and in the ply yarn. When the elastic component is a core-spun yarn, selection of proper direction of twist will improve the extent to which the elastic element is covered by the inelastic ply. When the elastic component is a blend of elastic and inelastic staple fibers, selection of the proper direction of twist will assist in looking the elastic staple fibers into the total yarn structure and will thereby minimize the likelihood of pilling and other undesirable fabric surface effects. For example, in preparing a yarn of the following twist combination:

Single Twist Direction Ply Twist Direction Elastic yarn I I Inelastic yarn S TABLE 4 Example XVII XVIII XIX XX XXI XXII No. of plies in final yarn--- 3 3 3 2 2. 2. Component yarns used X, Y, Z X, Y, Z X, Y, Z... Y, Z X, Y X, Z. Stretch varied during plying for X X, X an Z Both Both Both.

1 In unison and individually.

These yarns are woven individually as filling in a warp of yarn Y. It is esential to maintain the plied yarns under full tension until they are woven, in order to preserve their varied stretch characteristim. After finishing the fabrics display novelty surface effects dependent in each case on the particular composition and variable stretch characteristics of the filling yarn. The power level of all fabrics is high.

It will be apparent that the heat-set/ply procedure of the present invention can be used in various ways to facilitate the production of novelty elastic yarns and fabrics by the general manner just outlined. Among such applications are the following:

(a) Yarn X alone may be subjected to varying stretch then mildly heat-set before plying.

(b) Yarn X may be subjected to vraying stretch beit would be expected that the elastic yarn ply would tend to bury itself within the inelastic yarn ply to a much greater extent than if the twist in both component yarns was in the Z direction. Further, in plying such a yarn, the twist in the elastic yarn will increase while the twist in the inelastic yarn will decrease proportionally to the number of turns in the plied yarn. In this way, the elastic yarn will be more effectively covered because of higher twist and coring, while a desirably high bulk and softness of hand in the plied yarn will be maintained because of the low twist in the inelastic yarn ply. for dyed fabrics, an additional benefit of this procedure is that exact matching of shades dyed on the elastic and inelastic fibers is less critical because of the more effec tive cover of the elastic fibers and the reduced likelihood of their appearing on the surface of the fabric.

It will be apparent from the foregoing discussion and xamples that a number of alternative procedures may be ollowed in preparing the elastic component for use in he present invention. In addition to those procedures vlready mentioned, a continuous spandex filament may be teat-set by drafting the filament and winding it up on a )obbin or dye tube and then placing the bobbin or dye ube in an autoclave or oven. The heat-set filament may hen be used as the core in preparing a composite elestic arn by procedures described previously herein.

This invention can be employed wherever it is desired produce woven, knitted and non-woven fabrics having t relatively high degree of elasticity and a relatively low evel of power. Examples of such uses are universal itting apparel (socks, polo shirts, underwear, bathing illltS, gloves, elastic cuffs, sweaters, waistbands, suits, :oats, dresses, skirts, action sportswear, leotard-type outer wear, and accessories such as tapes, webbings, and other .voven, non-woven, or knit apparel fabrics), household products (form-fitting upholstery, slipcovers, sheets, carpets, mattress coverings, and narrow tapes and webbings for a wide variety of uses), industrial products (transportation upholstery, woven and non-woven felts, tapes and webbings for varied applications), and medical products (surgical bandages, supports, elastic dressings, surgical stockings, and splint tapes). In addition, high stretch, moderate recovery fabrics can be made suitable for use in outer apparel (sweaters, knit jersey, and woven, knit, or non-woven suitings and dress goods), household items (rugs, carpets and upholstery), and industrial products (woven, non-woven, and knit compression or impact-bearing structures). Illustrations of various specific products are shoe laces, shoe liner fabric, shoe upper fabrics, house slippers, skin diving suits, snow suits, ski pants, football pants, slacks, flannels, sport shirts, bulky knit sweaters, blankets, swimming pool covers, toupee bases, belts, suspenders, garters, watch bands, ropes, elastic sewing thread, shock cords, bookcover jackets, bookbinding cloth, synthetic paper, elastomer-coated fabrics, and super-dense felts, such as papermakers felts.

Fabrics made by this invention may be given the customary finishing treatments where necessary or desired, such as scouring, washing, drying, pressing, dyeing, and softening.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

. I claim:

1. A process for preparing elastic fabrics which comprises:

(a) stretching an elastic yarn containing spandex filaments a predetermined amount approaching but not exceeding the elastic limit of said elastic yarn;

(b) temporarily heat-setting under mild heat-setting conditions to initially stabilize the elastic component but permit retraction of from 30% to 60% when the final fabric is subsequently heat-relaxed, said elastic yarn in its extended condition;

(c) plying said heat-set elastic yarn with an inelastic Y yarn While maintaining said elastic yarn in a fully extended condition;

((1) incorporating said plied yarn in a fabric while maintaining said plied yarn in its fully extended state; and

(e) heat-relaxing said fabric to permit said elastic yarn to contract.

2. The process of claim 1 wherein said spandex filaments are continuous filaments and said heat-setting is carried out in steam.

3. The process of claim 1 wherein said elastic yarn is "comprised of a blend of inelastic and spandex staple fibers and said heat-setting is carried out in steam.

4. A process for preparing elastic fabrics which comprises:

(a) stretching an elastic yarn containing spandex filaments a predetermined amount approaching but not exceeding the elastic limit of said elastic yarn;

(b) plying said elastic yarn with an inelastic yarn while maintaining said elastic yarn in its extended condition;

(c) temporarily heat-setting under mild heat-setting conditions to initially stabilize the elastic component but permit retraction of from 30% to 60% when the final fabric is subsequently heat-relaxed, said plied yarn to heat-set said elastic yarn in its extended condition;

(d) incorporating said plied yarn in a fabric while maintaining said plied yarn in its fully extended state; and

(e) heat-relaxing said fabric to permit said elastic yarn to contract.

5. The process of claim 4 wherein said spandex filaments are continuous filaments and said heat-setting is carried out in steam.

6. The process of claim 4 wherein said elastic yarn is comprised of a blend of inelastic and spandex staple fibers and said heat-setting is carried out in steam.

References Cited by the Examiner UNITED STATES PATENTS 2,504,523 4/1950 Harris et al 57-140 2,728,973 1/1956 Kummel 28-71.3 2,771,757 11/1956 Burleson et a1 66-202 X 3,001,359 9/1961 Simon 57-157 3,007,227 11/1961 Moler 28-1 3,009,311 11/1961 Wang 57-152 3,011,302 12/1961 Rupprecht 57-152 3,038,295 6/ 1962 Humphreys 57-152 3,069,883 12/1962 Burleson et al. 66-178 3,077,006 2/ 1963 Ibrahim 28-1 3,078,653 2/1963 Marshall 57-152 3,098,347 7/1963 Smith 57-152 3,115,745 12/1963 Lathem et al. 57-163 3,166,885 1/1965 Bridgeman et al. 57-152 MERVIN STEIN, Primary Examiner.

DONALD W. PARKER, I. KEE CHI,

Assistant Examiners. 

1. A PROCESS FOR PREPARING ELASTIC FABRICS WHICH COMPRISES: (A) STRETCHING AN ELASTIC YARN CONTAINING SPANDEX FILAMENTS A PREDETERMINED AMOUNT APPROACHING BUT NOT EXCEEDING THE ELASTIC LIMIT OF SAID ELASTIC YARN; (B) TEMPORARILY HEAT-SETTING UNDER MILD HEAT-SETTING CONDITIONS TO INITIALLY STABILIZE THE ELASTIC COMPONENT BUT PERMIT RETRACTION OF FROM 30% TO 60% WHEN THE FINAL FABRIC IS SUBSEQUENTLY HEAT-RELAXED, SAID ELASTIC YARN IN ITS EXTENDED CONDITION; (C) PLYING SAID HEAT-SET ELASTIC YARN WITH AN INELASTIC YARN WHILE MAINTAINING SAID ELASTIC YARN IN A FULLY EXTENDED CONDITION; (D) INCORPORATING SAID PLIED YARN IN A FABRIC WHILE MAINTAINING SAID PLIED YARN IN ITS FULLY EXTENDED STATE; AND (E) HEAT-RELAXING SAID FABRIC TO PERMIT SAID ELASTIC YARN TO CONTRACT. 